The research is designed to determine whether lingual deafferentation results in reactive changes in the representation of gustatory or oral somatosensory responses in a first-order central relay, the nucleus of the solitary tract (NST), or its efferent targets. Central plasticity in the adult mammalian nervous system has been demonstrated to occur as a result of deafferentation in several sensory systems, including the trigeminal. Almost nothing, however, is known about the effects of oral deafferentation upon the other major central target of oral afferent projections, the NST, or higher levels of the neuraxis that receive information from this nucleus. The proposed experiments will utilize multiunit and single-unit recording techniques to determine if the topographic organization or responsiveness of NST neurons changes at different time periods following elimination of afferent input from the chorda tympani or glossopharyngeal nerves. In addition, immunocytochemical techniques for the detection of an inducible, immediate-early gene, c-fos, and for the inhibitory neurotransmitter, gamma-aminobutyric acid, will be used to determine whether deafferentation results in functional changes at other levels of the neuraxis as well. These experiments focus on the gustatory and oral somatosensory systems, and will elucidate central neural changes that may occur after peripheral nerve perturbations as a consequence of middle ear and third-molar surgery, or other types of damage resulting from trauma, diseases, or pathologies affecting cranial nerves innervating oral tissues. Elucidating the response of the central nervous system to peripheral deafferentation has implications for a variety of clinically-important conditions, such as dysgeusia and dysesthesia, as well as for chronic pain, which is hypothesized to involve central neural changes accompanying peripheral inflammation or deafferentation. Finally, these experiments will help to define general principles of neural reorganization after injury, which may have implications for functional studies of repair.